The present invention relates generally to image forming apparatuses, and more particularly to an image forming apparatus for forming an image corresponding to an subject. The image forming apparatus achieves a high resolution applicable to a high definition television.
Lately, the Japanese Broadcasting Corporation has been taking a leading role in developing a high definition television (called HDTV for short). The HDTV is also called a high resolution television, which requires more than one million picture elements (called pixels for short), about five times as many as in conventional televisions, and a frequency band width higher than 30 MHz. However, it is difficult to develop a solid-state image sensor having more than one million pixels and a clock frequency higher than 30 MHz. Accordingly, Japanese Laid-Open Patent Application No. 60-213178 has proposed an image forming apparatus having a plurality of solid-state image sensors. According to the image forming apparatus, an optical image is divided into a plurality of optical images corresponding to the number of solid-state image sensors so that each of the optical images is received by a corresponding solid-state image sensor. Then each of the optical images is piled by means of shifting the pixels of each solid-state image sensor a predetermined pitch apart according to the pixel shifting method disclosed in Japanese Patent Publication No. 56-40546. But the image forming apparatus according to the reference No. 60-213178 has the following disadvantages:
1. The proposed image forming apparatus must pile the pixels of each solid-state image sensor so that they are shifted a predetermined pitch apart which is difficult to accomplish. For example, the solid-state image sensors must be shifted several um apart from one another to a precision 1/10, which value tends to be negatively influenced by thermal expansion thereof;
2. The substantial resolution of the proposed image forming apparatus is not as improved as described in the specification thereof because each of the pixels are partially piled, as mentioned above.